A door trim for an automobile, for example, typically consists of an upper door trim, a lower door trim, and the like. The upper door trim may be a laminated structure having a plastic core and a surface film adhered on it. The lower door trim may be an injection-molded plastic. To form a joint for the upper door trim and the lower door trim, a semifinished or semi-assembled product is used. The semifinished product is prepared by inserting bosses for welding, which are vertically arranged with appropriate intervals along the lower door trim edge, into mounting holes formed in the upper door trim. The semifinished product is set in an ultrasonic welding and caulking equipment. Then welding (ultrasonic welding and caulking) is performed by closing a clamping device to join the upper door trim and the lower door trim (see JP-A-2004-224012).
When performing the ultrasonic welding as described above, a gap between the boss for welding and the periphery of the mounting hole may cause a gap between the upper door trim and the lower door trim, to thereby lessen their contact. Therefore, during the ultrasonic welding, the area near the welding should be held tightly. In an assembly line (fabrication line), various processes such as bending a pawl for a weather strip, retainer-inserting, and screwing, as well as ultrasonic welding, are performed by respective equipment.
A supporting jig for a semifinished product inside the ultrasonic welding and caulking equipment, the pawl-bending equipment, the retainer-inserting equipment, and the like, in the traditional assembly line has a special part for each joint of each respective process. A holder of the supporting jig for the joint part may also be formed in accordance with the number of joints to be processed by each equipment.
Since each equipment uses a respective jig and a holder, a supporting jig for one equipment cannot be used by another equipment, and a machine for the transportation of the semifinished product between processing equipment is required. Therefore, there are problems, such as difficulties in improving productivity and increased assembling costs. The increased assembling cost of each equipment is also a problem, because of a need for making a respective supporting jig for each product.
Although a traveling carriage can be used for positioning a work on a support and for clamping it there, a traditional traveling carriage is heavy, because a clamping means is mounted on it. Thus, the difficulty in using such a carriage in an assembly line is a problem.